Shrink micrometer calipers



May 7, 1957 H. c. HANDY 2,791,034

: SHRINK MICROMETER CALIPERS Filed June '16. 1953 i. l .J

flrea of JIeeVe By? 4. v I

Afforneys United States Pater-n SHRINK MICROMETER CALIPERS Howard C.Handy, Springfield, Mass.

Application June 16, 1953, Serial No. 362,015

2 Claims. (Cl. 33-166) The present invention relates in general tomicrometer calipers and more particularly to an improved micrometercaliper, the readings of which include shrinkage allowances for varioustypes of metals whereby the measurements of patterns, master patternsand transfer patterns for use in making castings of iron, brass, bronze,aluminum and other metals may be read directly from the micrometer.

An object of the invention is to provide an improved caliper, the scaleof which includes shrinkage allowances corresponding to the shrinkagefactor of a particular metal.

A further object of the invention is to provide an improved caliper, thescale of which may be readily changed to correspond to the shrinkagefactor of a particular metal.

A still further object of the invention is to provide a micrometercaliper having interchangeable sleeves, the scales of which includeshrinkage allowances corresponding to the shrinkage factors of varioustypes of metal.

A still further object of the invention is to provide a micrometercaliper having a set of interchangeable sleeves, each sleeve havingthereon a zero line which includes shrinkage allowances corresponding tothe shrinkage factor of a particular metal.

Other objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

Fig. l is a side elevation of a micrometer caliper, the sleeve of whichhas a pattern shrinkage-measurement zero line;

Fig. 2 is a vertical longitudinal section of the sleeve and thimbleassembly of Fig. 1;

Fig. 3 is a perspective view of an interchangeable sleeve provided witha single pattern shrinkage-measurement zero line;

Fig. 4 shows the development of the zero line of a sleeve; and

Fig. 5 is a side elevation of an oversize micrometer caliper providedwith one of the interchangeable pattern shrinkage-measurement sleeves.

In general, metal castings are made by either of two methods, namely, ina sand mold using a wooden pattern, or in a metal gate-mold which,itself, has been formed in a sand mold. In the first instance, alldimensions of the wooden pattern must be increased over the finaldimensions of the cast metal article by an amount corresponding to theshrinkage factor of the particular metal being used, that is to say, ifthe cast article is to be made of brass, bronze or aluminum, then themeasurements of the wooden pattern must be increased by substantially0.0156 inch per inch, which, for clarity is referred to as the shrinkagefactor of these metals. If the cast metal is cast iron, then themeasurements of the wooden pattern must be increased by .0104 inch perinch, which is the shrinkage factor of cast iron. In instances where ametal gate-mold is used to make the dual casting, the measurements ofthe wooden pattern for casting the metal gate-mold must allow for boththe shrinkage of the metal of the gate-mold itself and the shrinkage ofthe metal of the finished casting made in the metal gate-mold, that isto say, allowance must be made for double shrink. Moreover, it isapparent at once that the allowances for double shrinkage will vary,depending upon the types of metal involved. For example, the metalgate-mold may be formed of cast iron, while the casting to be made inthe metal gate-mold may be bronze. Thus, in making the wooden patternfor the metal gate-mold, the dimensions of the wooden pattern must beincreased to allow for the shrinkage factors of both the cast iron andthe bronze.

Among pattern makers, it is the practice to use a conventionalmicrometer caliper for checking the measure ments of a wooden pattern,the final dimensions of which are arrived at by mentally adding ashrinkage allowance to each basic dimension of the pattern. Thispractice is not conducive to accuracy of measurement in the finishedpattern and has, in fact, resulted in many costly mistakes and waste ofmaterials.

The present invention is the concept of providing a plurality ofseparate but interchangeable sleeves for a conventional micrometercaliper, each sleeve having a scale thereon, sometimes referred tohereinafter as a zero line, the readings of which include shrinkageallowances which are characteristic of a particular type of metal. Thus,by equipping a standard micrometer caliper with an interchangeablesleeve of this type, the pattern maker may mike a wooden pattern andread directly from the zero line of the micrometer caliper a measurementwhich will allow for the shrinkage factor of a particular metal such as,for example, cast iron. If, thereafter a wooden pattern is to bemeasured for making a bronze casting, then the sleeve having readingscorresponding to the shrinkage factor of cast iron is removed andreplaced by a sleeve having readings corresponding to the shrinkagefactor of bronze. In order to permit such interchange of sleeves, theconstruction of each is identical except for the zero line inscribedthereon. It is therefore apparent that when applied to a sleeve the terminterchangeable means that the particular sleeve mounted on the frame isadapted to be replaced by another sleeve whenever a change in thematerial to be cast requires a different shrinkage factor to be employedin measuring the pattern from which the casting is to be made.

The readings of the zero line of each sleeve will include the basicdimension of the pattern plus an amount corresponding to the shrinkagefactor of a particular metal. For brevity, these readings are referredto as the pattern shrinkage-measurements.

Referring to the drawings, Fig. 1 discloses a micrometer caliper whichcomprises a frame 10 having a fixed anvil 11 at one end in axialalignment with which is a longitudinally movable spindle 12 whichextends through an axially aligned aperture 13 in the opposite end ofthe frame and carries a thimble 14 at its outer or right-hand end, asviewed in the drawings for rotating the spindle 12.

Rigidly secured to or integral with frame 10 is a tubular extension orbarrel 15, which is axially aligned with the aperture 13 and spindle 12.The end of barrel 15 adjacent thimble 14 is internally threaded toreceive a spindle nut 16 which is threaded both internally andexternally. The outer end of the spindle 12 is provided with externalscrew threads which, as shown especially well in Fig. 2, are threadedlyengaged in spindle nut 16. By rotating the thimble 14, the spindle 12will thus be made to move longitudinally relative to the fixed anvil 11.

The external th ads at the outer earl of spindle nut 16 taper outwardly,and the spindle nut is slotted longitudinally at the end to permit it tobe constricted slightly by an adjusting nut 17. This is a common methodof taking up any wear between the threads of the spindle 12 and theinternal threads of the spindle nut 16.

An interchangeable sleeve 18 fits snugly over the barrel 15 with one endabutting the shoulder 19 of frame 10. In order to prevent sleeve 18 frombeing inadvertently moved longitudinally or rotated on barrel 15, abarrel spring 20 is provided in a recess in barrel 15 so that itfrictionally engages the inner surface of sleeve 18 to permit it to bemoved only by means of a tool such as a pair of pliers. The thimble 14is provided with a beveled edge at its inner end, which edge has avernier scale marked thereon in conventional manner.

A characteristically novel feature of the invention is the provision ofinterchangeable sleeves 18 having zero lines, the readings of whichinclude shrinkage allowances corresponding to the shrinkage factors ofdifferent types of metal. However, it will be appreciated that otherforms of means for detachably securing the sleeves to the frame of themicrometer may be used than that shown and described hereinabove. It isintended, moreover, to provide sleeves having scales in accordance withthis invention for any of the various common types of micrometers inwhich the sleeves may be removed. Furthermore, micrometers which do nothave detachable interchangeable sleeves, but which incorporate a scaleembodying the inventive concept hereinafter disclosed, are clearlywithin the purview of the invention.

As in conventional micrometer calipers, the pitch of the screw threadson the thimble-end of the spindle 12 is forty to an inch, so that onecomplete revolutionof the spindle moves it longitudinally ,4 ortwenty-five thousandths of an inch. The zero line on the sleeve 18 ismarked in increments of twenty-five thousandths, plus an increment of aparticular shrinkage factor, in the manner hereinafter described, whilethe beveled edge of the thimble 14 is divided into twenty-fivedivisions, every fifth line being numbered. Rotation of the thimble fromone of its divisions to another will move the spindle longitudinally oftwenty'five thousandths or one one thousandth of an inch plus anincrement of a particular shrink age factor.

Referring especially to Fig. 3, each interchangeable sleeve of themicrometer caliper is provided with a zero line, the readings of whichinclude a shrinkage allowance corresponding to the shrinkage factor of aparticular metal. The zero line of a conventional micrometer calipersleeve is substantially straight and divided into forty lines to theinch corresponding to the number of threads on the spindle. The zerolines of the interchangeable sleeves of this invention are similarlydivided into forty substantially equal divisions, but the zero lines aresubstantially helical and the forty divisions of each zero line extendover a distance of one inch plus a shrinkage allowance corresponding tothe shrinkage factor of a particular metal. For example, if aninterchangeable sleeve is for use in measuring patterns for brass,bronze and aluminum castings wherein the shrinkage factor issubstantially 0.1875 inch per foot or 0.0156 inch per inch, then theforty divisions on the helical zero line of an interchangeable sleevespan a length of one inch plus 0.0156 inch.

The development of the zero line on the sleeve, such that each divisionof the zero line will equal twenty-five thousandths of an inch plus anincrement of the shrinkage factor, is geometric in principle and can bedone in any one of several ways. For example, referring to Fig. 4 whichrepresents a sleeve opened up, and assuming by way of example ashrinkage factor of 0.0104 inch per inch, this means then that in makinga measurement of one inch on a pattern, the thimble will be turned outuntil the distance between the fixed anvil and the adjacent end of thespindle is exactly 1.0104 inches at which time the zero of the thimble,indicated at t in Fig. 4, would be in advance of the zero line of anordinary micrometer sleeve by an angular amount indicated at a in Fig. 4and corresponding to 1.0104 inches of travel longitudinally of thesleeve. Now by dividing the distance a into the number of divisionsdesired on the zero scale, which in the example shown is forty, anddrawing horizontal lines from each of these divisions transversely tointersect a diagonal line connecting the zero 0 of the scale, with thezero I of the thimble, a zero line 2: is formed which is divided intoforty equal increments each equivalent to twenty-five thousandths of aninch plus one fortieth of the increment of 0.0104 inch. When this openedsleeve is made cylindrical, the zero line 1 has a helical form such asshown in Fig. 3.

The development of the Zero line on the interchangeable sleeves may becarried out in substantially the same way for sleeves which are to beused in measuring patterns for castings of other types of metals suchas, for example, brass, in which case the shrink factor is 0.0156 inchper inch.

Further, the Zero line of a sleeve may be developed for use in makingdirect pattern shrinkage-measurements of double shrinks as, for example,when casting a metal gate-mold. If the metal gate-mold is to be made ofcast iron and to be used for forming cast iron castings, then theshrinkage factor is double that for a single cast iron shrink or 0.0208inch per inch. On the other hand, if the metal gate=mold is to be madeof aluminum for use in forming cast iron work-pieces, then there will bea double shrinkage factor which is equal to the 'sum of 0.0156 inch perinch for the aluminum and 0.0104 inch per inch for the cast iron or0.026 inch per inch. In each of the foregoing instances, the developmentof the zero line on an interchangeable sleeve of the micrometer caliperis carried out in the manner hereinabove described.

While Figs. 1 through 4 serve to illustrate the invention as applied toa one-inch micrometer, the invention is applicable also to micrometershaving a relatively large frame such as shown in Fig. 5. Microrneters ofthis size are provided with interchangeable anvil's such as illustratedat 21 to increase the range of usefulness of the micrometer. The terminterchangeable as applied to anvil 21 means that each anvil may bereadily replaced in frame 10 by another anvil of the same constructionbut having a different length to compensate for a desired change in therange of measurement. Where a micrometer having a range of from one inchto six inches is used for measuringfrom zero to one inch, 21 standardfive inch interchangeable anvil is used in conjunction with aninterchangeablesleeve such that the distance between the end of theanvil and the opposite end of the spindle will be substantially one inchplus the allowance for shrinkage when the thimble has been turned to theten position on the zero line of the sleeve.

It will be noted that the zero line of each interchangeable sleeve isdeveloped on the basis of the amount of shrink per inch. Consequently,when measuring distance greater than one inch, additional allowance mustbe made for the shrinkage factor. For example, cast iron has a shrinkfactor of substantially 0.0104 inch per inch, which for two inches wouldbe 2 0.0l04, or 0.0208 inch. In adapting the shrink micrometer of Fig. 5for measuring from one inch to two inches, in conjunction with a sleevehaving a zero line for cast iron shrinkage factor, an interchangeableanvil 21 would be used, the over-all length of which would besubstantially four inches minus 0.0104 inch. Thus", when the thimble isretracted to its number ten division of the sleeve, the total distancebetween the end of the anvil and the corresponding end or" the spindleis substantially 2.0208 inches.

Similarly, for measurements between zero and three inches, the shrinkagefactor for cast iron will be 3 0.0104 or 0.0312 inch per inch. Hence,the length of the interchangeable anvil 21 will be three inches minus0.0208 inch, so that when the thimble is fully retracted,

the total distance between the end of the anvil and the end of thespindle will be 3.0312 inches.

In brief then, to use the micrometer caliper for measuring a woodenpattern to be used in making an iron casting, the pattern maker checkshis micrometer to see that it is provided with an interchangeable sleevehaving a zero line characterized by shrinkage allowances correspondingto the shrinkage factor of cast iron. If it is so equipped, he may thenmeasure his wooden pattern and read the measurements directly from thehelical zero line of the sleeve knowing that each measurement makesallowance for the shrinkage factor of cast iron. Should he then wish touse the micrometer for making measurements of a pattern to be used informing a casting of a different type of metal, such as, for example,brass, bronze or aluminum, the pattern maker then disasscmbles themicrometer and replaces the interchangeable sleeve by one having a zeroline characterized by shrinkage allowances corresponding to theshrinkage factor of brass, bronze or aluminum. If measurements greaterthan one inch are to be made, he must also be sure to have the properanvil which will allow for shrinkage of the particular metal for eachinch in excess of one. After reassembling the micrometer, the patternmaker may then proceed to measure the wooden pattern with the assurancethat each measurement makes allowance for the shrinkage factor of brass,bronze or aluminum. Although cast iron and such metals as brass, bronzeand aluminum have been mentioned, it will be appreciated that a singlemicrometer may be readily converted for making direct measurements ofthe patterns for use in casting these as well as other types of metals,that is to say, by providing a micrometer with four, five or even moreinterchangeable sleeves and anvils, a single micrometer may be used toaccurately measure patterns for a large variety of metals.

In assembling the sleeve on the micrometer, the sleeve 18 is worked overthe barrel 15 with the spring 20 in place until one end of the sleeve isin firm abutment with shoulder 19 of the frame 10. This may be done byusing a pair of pinchers or pliers having jaws made of a comparativelysoft material for gripping the sleeve without damaging its surface. Thesleeve is then rotated on the barrel by means of the pinchers toapproximately its correct relative position withrespect to the frame ofthe micrometer. This position may be indicated by reference marks on theframe and sleeve respectively, which marks are lined up in order toquickly arrive at the approximate positioning of the sleeve. The patternmaker then corrects this setting in the same manner that is used inassembling conventional micrometers, that is, by turning the spindle upagainst the anvil and noting the reading of the zero on the thimble withrespect to the 0 on the scale of the sleeve. The spindle is then backedoff and the sleeve rotated in the proper direction by means of thepinches an amount equal to the initial error and the setting againchecked. This is continued until an ac curate reading is made.

Although the zero lines of the interchangeable sleeves have beendeveloped on the basis of the English system of measurement, it will beunderstood that the same principle may be used to develop a zero linebased on the metric system. Further, although the patternshrinkagemeasurement scales are shown used on interchangeable sleeves ofa micrometer caliper, it will be understood that it is within thepurview of the invention to provide other types of gauges withinterchangeable pattern shrinkagemeasuring sleeves or the equivalent as,for example, vernier calipers, gauges, indicators, inside micrometers,height gauges and similar measuring instruments.

The invention may be carried out in other specific ways than thoseherein set forth without departing from the spirit and essentialcharacteristics of the invention, and the present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

I claim:

1. An instrument for measuring the dimensions of a master pattern intenns of the final dimensions of the castings to be produced from thepattern comprising a frame having an interchangeable anvil at one endthereof, an element movably mounted in said frame opposite saidinterchangeable anvil for movement longitudinally relative thereto, aninterchangeable cylindrical sleeve detachably secured to said framecoaxial with said element, a helical zero-line inscribed on the surfaceof said sleeve and divided into a plurality of dimensional readings,rotatable measuring-means secured to the end of said element beyond saidsleeve, a helical zero-line inscribed on the surface of said sleeve anddivided into a plurality of equal dimensional readings, saidinterchangeable anvil being of a predetermined length to correspond withthe total number of said divisional readings on said interchangeablesleeve and include a. shrinkage allowance dependent on the helicallength of said Zero-line, and a circumferential scale on the end of saidmeasuring-means adjacent said sleeve, said scale having a zero indexadapted to cooperate with said zero-line on said sleeve for readingshrinkage measurements directly therefrom, said helical zero-line beingformed with such slope that the longitudinal movement of saidmeasuring-means required to bring said zero index of saidcircumferential scale into correspondence with each of said dimensionalreadings exceeds the actual numerical value thereof by an amountequivalent to the shrinkage factor of the particular material from whichthe casting is to be made.

2. In a micrometer caliper for measuring the dimensions of a masterpattern in terms of the final dimensions of the castings to be producedfrom the pattern, the combination including a frame having aninterchangeable anvil at one end thereof, a spindle rotatably mounted inthe opposite end of said frame substantially in axial alignment withsaid anvil for movement longitudinally relative thereto, aninterchangeable cylindrical sleeve detachably secured to the spindle-endof said frame substantially coaxial with said spindle, a helicalzero-line inscribed on the surface of said sleeve and divided into aplurality of equal dimensional readings, rotatable measuring-meanssecured to the spindle-end of said frame, said interchangeable anvilbeing of a predetermined length to correspond with the total number ofsaid divisional readings on said interchangeable sleeve and include ashrinkage allowance dependent on the helical length of said zero-line,and a circumferential vernier scale on the inner end of saidmeasuring-means adjacent said sleeve, said scale having a zero indexadapted to cooperate with said zero-line on said sleeve for readingshrinkage measurements directly therefrom, said helical zero-line beingformed with such slope that the longitudinal movement of saidmeasuring-means required to bring said zero index of saidcircumferential scale into correspondence with each of said dimensionalreadings exceeds the actual numerical value thereof by an amountequivalent to the shrinkage factor of the particular material from whichthe casting is to be made.

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